OBJECTIVES: Physicians often make dosage decisions based on experience and heuristic factors in addition to the product label.  This makes it difficult for economists to compare the “real world” costs and benefits of alternative therapeutic choices.  We compare a published methodology for calculating therapeutic dose equivalence based on approved labeling for varous antipsychotics prescribed for schizophrenia with actual prescription data in that population.  METHODS: The sample consisted of a proportional selection of patients that derived from a population of patients of all ages, across all payers, and in all regions of the United States.  The information included NDC code sets, quantity, and day of supply and was aggregated from pharmaceutical prescriptions files.  The frequency distribution measured the top antipsychotic medications in patients diagnosed with schizophrenia.  The therapeutic dose equivalence was determined using the methodology of Woods (2003) as the comparator.  RESULTS: A total of 324,724 patients with a diagnosis of schizophrenia were included in the study.  Doses equivalent to 1 mg/day of Risperidone were 86.17 mg/day of Quetiapine, 5.09 mg/day of Olanzapine, 5.25 mg/day of Aripiprazole, 92.28 mg/day of Clozapine, and 33.74 mg/day of Ziprasidone.  CONCLUSIONS: With the ever-increasing array of differntially-dosed medications available, it is imperative for physicians and outcomes researchers to utilize estimation of therapeutic dose equivalence that reflects actual practice patterns so that informed decisions can be made evaluating the cost and cost-effectiveness of various therapeutic choice.  Our study enables pharmacoeconomic comparisons among antispychotics not only according to label-approved dosages, but also real-world dosing patterns.